Spot brake with removable friction pads



June 28, 1960 H. J. BUTLER 2,942,695

SPOT BRAKE WITH REMOVABLE FRICTION PADS Filed March 25, 1958 f? ffaz 21/ 24 I f w INVENT'OI? United States Patent 6 ice sjror BRAKE wrrn REMOVABLE FRICTION PADS Henry James Butler, Sutton Coldfield, England, assignor to Dunlop Rubber Company Limited, London, England, a British company Filed Mar. 25, 1958, Ser. No. 723,722

Claims priority, application Great Britain Apr. 1, 1957 14 Claims. (Cl. 188-73) This invention relates to disc brakes and is an improvement in, or modification of, the disc brake forming the subject-matter of US. application Serial No. 455,828, filed September 14, 1954, now Patent No. 2,921,650, dated January 19, 1960.

In the above patent I have described a disc brake comprising a rotatable disc, a non-rotatable bracket located adjacent the outer periphery of the disc, two pad-retaining members extending radially inwardly from each end of the bracket in circumferentially-spaced relation, a pad of friction material adjacent each side of the disc and an actuating mechanism for forcing the pads of friction material into frictional contact with the sides of the disc. The braket is so constructed that a portion may be removed to permit removal of the friction pads and associated pressure plates without dismantling the brake.

The above brake is particularly adapted for use in heavy vehicles such as railway rolling stock, and also in industrial machinery, wherein provision can be made for suitably anchoring the bracket which, as shown in the drawings of the above specification, is substantially of the cantilever type.

The present invention provides improvements in, and modifications of, the above brake which will render the brake more readily adaptable for use over a wider range of applications.

According to the present invention, therefore, a disc brake comprises an annular rotatable disc, a non-rotatable housing comprising a limb extending adjacent each radial surface of said disc, each limb comprising a fluid-pressure mechanism operable to force an associated friction pad into frictional engagement with said disc, means associated with each said limb to prevent movement of said friction pads in either tangential direction relative to said disc when the brake is applied, said means including means detachable from each said limb to permit removal and insertion of said friction pads in one said tangential direction.

Preferably said fluid-pressure operated means comprises a cylinder formed integrally in each said limb coaxially of a passage in which a friction pad is adapted to slide upon actuation of a piston slidable within said cylinder. Preferably, also, said piston is flared outwardly at the end thereof adjacent the associated friction pads, and this flared portion is truncated at opposite ends of a diameter to form two parallel chordal flat surfaces which are engaged by side flanges protruding from the rear of the friction pad. These flanges are preferably formed on a backing plate to which the friction pad is secured and have inturned portions adapted to be engaged in co-operating grooves formed in the chordal truncations of the end of the piston so that the friction pad is constrained to move axially in unison with the piston but may be detached therefrom or secured thereto by relative movement therebetween in a direction parallel to the plane of the disc and tangential thereto.

Preferably the detachable means permitting removal and replacement of the friction pads in a tangential direction comprises a portion of the peripheral wall of the pasage in each limb.

But a better understanding of the invention may be adjacent the outer periphery of a rotatable disc 4, and

the two arms or limbs 5 and 6 extending radiallyinwardly of opposite radial sides of the disc 4 in parallelspaced relation thereto. The limb 5 is of greater radial length than the limb 6 and at its radially-inner extremity is formed with a pair of circumferentially-spaced ears '7 which are adapted to be secured to a non-rotatable portion of a vehicle or other device.

Co-axial passages are formed axially through each limb 5 and 6, and each of these passages comprises a large diameter portion 9 (Fig. 2) on the side of the limb adjacent the disc 4 and a smaller diameter portion 10 on the axially-outer side of each limb, the portions 9 and It being co-axial with each other.

The portions of the larger diameter bore 9, one on each side of the disc, are each provided with a radiallyinturned rim 12 which provides an arcuate ledge extending radially into the bore portion 9 to provide a support and guide for the friction pads 13, later to be described. This rim 12 is shown in Figure 2 as being on the radiallylowermost side of the housing 1 whenthe housing is assembled in association with the disc 4. This position is subject to some variation in accordance with the positioning of the housing 1 relative to the disc 4 and with the normal direction of rotation of the disc 4 as shown by the arrow 3 of Figure 1, and is preferably orientated in relation to the disc 4 so that it is squarely presented to the normal direction of rotation of the disc, on the trailing side of the housing (i.e., the rear side of the housing relative to said rotation) for a reason which will be obvious as this description proceeds.

A closure member 14, fitted with an annular sealing ring '15, is secured in the axially-outer end of each bore portion 10 by means of a'circular spring clip 16 which is received in an annular groove in the outer end of the bore 10 and in an annular recess in the outer periphery of the closure member 14, the adjacent end portion 17 of the closure member 14 being peened over the spring clip 16, to lock the closure member 14 in the bore 19, when the respective parts are initially positioned.

With the closure member 14 in position, the bore 10 becomes a cylinder, by which name it will be identified henceforth in the following description, and in this cylinder 10 a piston 18 is fluid-tightly slidable.

The piston 13 is a cylindrical member comprising a small diameter portion 19 lying adjacent the inner face of the closure member 14. On the disc side of the portion 19 is formed an annular groove in which is located On the disc side of the portion 21 the piston is again" 1 reduced in diameter to a further cylindrical portion 22" (Figure 2) which is of substantially the same diameter Patented June 28, 1960 as the portion, 19 and is axially separated from the porthe inner peripheral bead of an annular flexible frustoconical. diaphragm 24 :which is disposed side facing. towards: the: disc 4.

The portion 22 of the piston 18- is-then-flaredradially outwardly into a. large diameter portion 25- which is located-within the bore portion 9 and is freely slidablc therewithinbetween the annular step-26 formed at the junction of the cylinder: 10 and the bore:portion- 9 and 'theinner. radial face. of the rim. 12. The outer peripheral. bead.27 of.-. the diaphragm 24 is-located between the step 26 and the flared portion of the pistonltiand providesa'dirtand moisture'seal for the cylinder 1G.

The flared end 25 of the pistont18'is truncated at each end-ofzone diameter: thereof toprovide'a' pair of diametrically-opposed parallel i fiat. surfaces 2-8 on chords thereof, and two-diametrically-opposed arcuate. surfaces 2 comprising the; peripheryof theiiared portion 25, the

surfaces 29 being co-axial of'the piston. 18, and being V loosely slidable within the. bore portion 9.

'A'- groove is: formed downieach fiat surface 28 par.-

allelwith, and. adiecent the radial. surface: of. the end of the fiaredportioni, and. into-the groove 3% is adapted to-be. slim-transversely of the portion 25,,the radiallyends 34' the diameter of which is somewhat less than the diameter across the corresponding arcuate surfaces 29 of thepiston 18. Thus, when thepad 13 and'baoking plate 32 are diametrically centered on the end of the piston 13 two diametrically-opposed portions of the flared end 25- of the piston18, and comprising the arcuateends 29 V of the baserof the piston, protrude beyond each arcuate end 3'4-of the friction pad 13 andbacking plate 32.

.The frictionpad 13 is'secured to the backing plate 32 a further rim 37, later to-be described, it isnot nece sary for the bond' between thebacking plate and friction pad to be such as to withstand any great shearing stresses.

One circumferential side of each bore 9 iscut away to form anaperture extending'to the outside of the'respective limbs 5. and 6, substantially tangentially of the disc 4 and diametrically-oppositethe rim 12, and is bounded byradially-spaced parallel walls'38, 39 each of which lies tangentially of the disc 4.

'The closure member 14, piston 18 and diaphragm 24 are inserted into each cylinder 10 and the housing 1 is then assembled in relation'to the disc 4 and the pres-* sure-fluid conduits are suitably connected to the cylinders 10 and a source of fluid-pressure (not shown) in The pistons 18'are orientated in the the known manner. cylinders 10 so that the fiat surfaces 28 lie substantially paralleLto a tan-gent of the disc 4 and one portion 35 of ea'ch piston 18 lies behind the arcuate rim 12 within each bore 9.

The pistons 18 are then pressed fully into the cylinde'rs' 10 so that the grooves 30 just protrudebeyond the innerfaces'41 of'thelirn'bs' Sand 6, the flanges 31 of the backing plates32 are engaged with the grooves3i) and the backin'gfpla't'es 32' and associated friction pads 13 are pressed" into the spaces between the=walls- 38' and 39 of the'limbssa'nd 6 o'f theU-sha'ped housing 1, the flanges BI sIiding inth'e grooves SU untiLtheradially-inner arcuwith its: concave vtion 21 by an annular recess 23 into which is inserted by any known suitable means, such as by adhesives,- by bonding, by" moulding in situ, or the like, and the backing platemay be perforated as at'36 to rcduce the heat 7 transferto the piston whenthe brake is-a'pplied. As the frictionpads '13 are supportedin shear'by the rim 12 and 4 during. braking when the vehicle is in reverse, a yoke member 42 is provided to comprise a removable guide and supportfor each pad 13. Eachyoke 42cotnprises an arcuate recessed portion 43, which, when the yoke 42 is in its position in the housingcompriss a circumferential continuation of the bore portion At one end of the recess. 43 there-is" provided the previouslymentionedg radial .rim portion37 which, .when the yoke 42 is in posi tiorr, lies. diametrically-opposite, and in'rco-axial' sym metry'with; the rim I2" and thus providesa guide support for the opposite arcuate surface 34 of the pad 13. The circumferentially-spaccd.endssofEthereceSs 43 are bounded by parallel lips 44,.which.when the yoke 42 is inserted into tliehousing; pass between the walls 38 and 39, of

V the limbs 5 and 6? of. the u shapedhousing 1 to hold the piston 13 and friction pad 13 against rotation and to provide a rigid support for the yoke 42,'WhjCh is detachably secured to the: limb" SE01: 6 by'abolt"45rwhichzisi passed axially inwardly through a: hole 46' in: the? limb 5: or 6,- and is engaged with a screw threadi in a hole 47: in the: shank 43 of theyoke. 42.

In the operation of the brake, pressureefiuidis passedl through? the conduits. 40 by actuatiorrofiat suitable; fluidpressure actuator suchv as a'rkn'own: type; of: master: cylin= der or, in: the case ofa constantly-pressurised system. as:

known in the art, byactuation: of a; suitable: fiuid. valve.

Fluid-pressure is; thus built up in". the annular spaces 49 in the'cylinders'? 19, betweerr the. clbsurememben 14- and the" piston sealing rings120, and? the pistons-'18 are:

moved axially inv the cylinders 10 towards! the disc: 4,.

forcing the friction pads 13 into? frictional engagement therewith. Thearcuate' ends 34 of'the:pads.13rslide:between the: rims E2- and- 37 andthe: torque: forcesiproducecf by braking are thus transferredlto the. rim: 12 or. 37

which lies on the side of the housing 1' away. fromiwhich.

the bolts 45' and yokes 42 and'the=sliding of the backing.

at'e ends 34' ofithe pads '13 engage the arcuate surfaces 1 ofithe rims 1-2;

-To support the friction pads 20 against dislodgement plates 32'and associated pad remnantsout of'the grovesi. 39in a direction tangential-ofthe disc 4; The pistons are then pressedback into the cylinders 10 until the groovesSfljust protrude beyond=the surfaces 44 and another backing plate'32 and pad-20 is then slid into" each pair'of grooves' 30, the yokes 42beingthenreplaced'as previously described; I

By providing means permitting the pads 13 to be=re=- moved tangentiallyofthe disc14 it is possible to produce a brake having readily-replaceable frictionpadswith out it being necessary to reduce the" axial width of the base member 1,, and thereby to increase the. bending moment of this member uuderbraking loads;

Having now described my inventionwhat'Iclaimis:'

1. A disc brake comprising a disc, 21 U'-shape'd housing having the. base oftl'ie U extending, axially adjacent the outer. periphery. of. the: disc. and' its limbs extending radially inwardsonopposite sides ofthe-dis cs each limb having, a cylinder bore: formed. therein, a. separate. and. separable yoke secnred=to each. limb of. the housing and defining with said limba pair: of guides. located. respectively on opposite sidesofia. radius. of-Isaid disc,,a-piston. in: each bore, a friction. pad; assembly in each pair. of:

guides, and means for: connecting. each. said assemblyto the adjacent piston for. axialtmovement. of the. connected.

piston: andassembly; together, said means enablingv the assembly to be withdrawn from'the connected piston g tangentially of the disc When the respective yoke is separated from the housing.

2. A disc brake as claimed in claim 1 wherein said pistons each have an enlarged head located adjacent the disc, each head having parallel grooved edges, and said assemblies each include a backing plate having parallel hooked flanges which engage in said grooved edges.

3. A disc brake as claimed in claim 2 wherein each of said assemblies consists of a pad of frictional material of the same shape as the backing plate, and the latter is perforated to minimize heat transfer from the pad to the adjacent piston.

4. A disc brake as claimed in claim 1 wherein each pad assembly has two fiat sides parallel to a tangent of the disc, and convex ends.

5. A disc brake as claimed in claim 4 wherein the guide surface in each limb and in each yoke is so shaped and located that said ends of each assembly and end portions of the fiat sides of each assembly are slidably engaged with said guide surfaces.

6. A disc brake as claimed in claim 1 wherein each yoke fits between the associated limb and the disc and has a tapped hole which registers with a plain hole in said limb, and a bolt extending through each plain hole is secured into said tapped hole to detachably secure the yoke to the limb.

7. A disc brake as claimed in claim 1 wherein the guide surfaces of the limbs and yokes are formed by the peripheries of radially extending lips located adjacent the disc.

8. A disc brake comprising an annular rotatable disc, a non-rotatable housing embracing a part of said disc and having a limb on each side of said disc extending from a part of the housing beyond the rim of the disc toward the center of the disc, each limb having a friction pad receiving recess extending axially from the face of the limb opposite a radial face of the disc and having a slot extending from said recess and open to said face, a friction pad in each friction pad receiving recess, an operating means on each limb acting on its respective friction pad to move the pad to frictional engagement with said disc, said recess and said yoke having guiding surfaces to abut the axially extending surfaces of the friction pad for guiding said friction pad axially as it moves to and from said disc and to support it against movement transverse to said axial movement.

9. The brake disc of claim 8 in which said slot extends in a direction transverse to a radius of said disc.

10. The brake disc of claim 8 in which said operating means comprises a fluid operated means coaxial with said recess to move a friction pad toward said disc.

11. The brake disc of claim 8 in which said operating means comprises a cylinder and piston in said limb axially aligned with said recess, said piston extending into said recess to engage said friction pad.

12. The brake disc of claim 11 in which said piston has grooves to engage a friction pad assembly and extending in the direction of said slot.

13. The disc brake of claim 8 in which said yoke has a pair of arms to receive a portion of a brake pad and a pad guiding surface between said arms.

14. The disc brake of claim 8 having a screw extending through said limb into engagement with said yoke.

References Cited in the file of this patent V UNITED STATES PATENTS 2,799,367 Dotto July 16, 1957 2,820,530 Chouings et a1. Jan. 21, 1958 FOREIGN PATENTS 1,117,453 France Mar. 23, 1956 738,545 Great Britain Oct. 12, 1955 

